Sudoite

Sudoite
General
Category	Phyllosilicate minerals
Group	Chlorite group
Formula	Mg2Al3(Si3Al)O10(OH)8
Crystal system	Monoclinic
Identification
Color	White to light green
Mohs scale hardness	2.5–3.5
Luster	pearly, dull
Refractive index	nα = 1.581 à 1.583 nβ = 1.584 à 1.589 nγ = 1.591 à 1.601
Birefringence	biaxial (-) ; δ = 0.010 to 0.018 2V = 64 to 70° (measured) 2V = 68 to 72° (calculated)
References	[1] [2]

Sudoite is a mineral from the chlorite group. It was named after Toshio Sudo (1911-2000), professor of mineralogy at the University of Tokyo, in Japan, and a pioneer of clay science. ^[3] The mineral tosudite also bears his name. It was approved as a valid species by the International Mineralogical Association in 1966.

Characteristics

Sudoite is a clay mineral with chemical formula defined as Mg₂Al₃(Si₃Al)O₁₀(OH)₈. It has a monoclinic crystal system. Its hardness on the Mohs scale is between 2.5 and 3.5.

Classification

Following the Nickel–Strunz classification, it is contained in the "09.EC.55" group:

Members of the 9.EC.55 group

Mineral	Formula	Symmetry group	Space group
Baileychlore	(Zn,Al) 3[Fe 2Al][Si 3AlO 10](OH) 8	1 or 1	C1 or C1
Borocookeite	Li 1+3xAl 4-x(BSi 3)O 10(OH,F) 8 (x ≤ 0,33)	2/m	C2/m
Chamosite	(Fe,Mg,Fe) 5Al(Si 3Al)O 10(OH,O) 8	2/m	C2/m
Clinochlore	(Mg,Fe) 5Al(Si 3Al)O 10(OH) 8	2/m	C2/m
Cookeite	LiAl 4(Si 3Al)O 10(OH) 8	1, 2 or 2/m	C1, C2 or Cc
Donbassite	Al 2[Al 2,33][Si 3AlO 10](OH) 8	2/m	C2/m
Franklinfurnaceite	Ca(Fe,Al)Mn 4Zn 2Si 2O 10(OH) 8	2	C2
Glagolevite	NaMg 6[Si 3AlO 10](OH,O) 8·H 2O	1	C1
Gonyerite	Mn 3[Mn 3Fe][(Si,Fe) 4O 10](OH,O) 8		unknown
Nimite	(Ni,Mg,Fe) 5Al(Si 3Al)O 10(OH) 8	2/m	C2/m
Odinite	(Fe,Mg,Al,Fe,Ti,Mn) 2,5(Si,Al) 2O 5(OH) 4	m	Cm
Orthochamosite	(Fe,Mg,Fe) 5Al(Si 3Al)O 10(OH,O) 8		unknown
Pennantite	Mn 5Al(Si 3Al)O 10(OH) 8	2/m	C2/m
Sudoite	Mg 2(Al,Fe) 3Si 3AlO 10(OH) 8	2/m	C2/m

Formation

It has been first discovered in the Knollenberg Keuper formation, in the village of Plochingen, Stuttgart Region (Baden-Württemberg, Germany). ^[4] Despite being an unlikely mineral, it has been described in every continent but Antarctica and Oceania. It is found mainly in hydrothermal or high-pressure/low-temperature (HP/LT) metamorphism contexts ^{[5] [6] [7]}

Use

This mineral has been used as gemstone for the production of personal ornaments, beads and pendants, during the Early Ceramic Age (500 BC – 500 AD), in the Lesser Antilles. ^[8] The precise source of such formation of sudoite allowing to carve artifacts in rather large blocks remain unknown.

References

1. Sudoite mineral information and data Mindat
2. Sudoite Mineral Data Webmineral
3. Kohyama, Norihiko (2000). "In memory of Prof. Toshio Sudo". Clay Science. 11 (2): 103–105. doi:10.11362/jcssjclayscience1960.11.103.
4. v. Engelhardt, W.; Müller, Germ; Kromer, H. (1962). "Dioktaedrischer Chlorit ("Sudoit") in Sedimenten des Mittleren Keupers von Plochingen (Württ.)". Naturwissenschaften. 49 (9): 205–206. Bibcode:1962NW.....49..205V. doi:10.1007/BF00633957. ISSN   1432-1904. S2CID   21590699.
5. Fransolet, André-Mathieu; Bourguignon, P. (1978). "Di/trioctahedral chlorite in quartz veins from the Ardenne, Belgium". The Canadian Mineralogist. 16 (3): 365–373.
6. Goffé, Bruno; Michard, André; Kienast, Jean Robert; Le Mer, Olivier (1988). "A case of obduction-related high-pressure, low-temperature metamorphism in upper crustal nappes, Arabian continental margin, Oman: P-T paths and kinematic interpretation". Tectonophysics. The Ophiolites of Man. 151 (1): 363–386. Bibcode:1988Tectp.151..363G. doi:10.1016/0040-1951(88)90253-3. ISSN   0040-1951.
7. Ruiz Cruz, María Dolores; de Galdeano, Carlos Sanz (2005). "Compositional and structural variation of sudoite from the Betic Cordillera (Spain): a TEM/AEM study". Clays and Clay Minerals. 53 (6): 639–652. Bibcode:2005CCM....53..639C. doi:10.1346/CCMN.2005.0530610. hdl: 10261/18786 . S2CID   52107572 . Retrieved 2018-10-20.
8. Queffelec, Alain; Bellot-Gurlet, Ludovic; Foy, Eddy; Lefrais, Yannick; Fritsch, Emmanuel (2021). "First identification of sudoite in the Caribbean Ceramic Age lapidary craftsmanship". Gems and Gemology. 57 (3): 206–226. doi: 10.5741/GEMS.57.3.206 . S2CID   245282849.

attribution translated from fr:Sudoïte